Rational design of phosphorus-doped cobalt sulfides electrocatalysts for hydrogen evolution

Moderate anionic doping is an effective approach to improve the performance of electrocatalysts toward hydrogen evolution reaction (HER) since it can adjust the electronic structure, active site, and phase. The reported studies mainly focus on designing P doped CoS₂, while other phases of cobalt sulfide, such as Co_1-xS and Co₉S₈ doped with P are rarely investigated for HER electrocatalysts. Herein, various cobalt sulfides (including CoS₂/Co_1-xS, Co_1-xS, and Co₉S₈) doped with P are anchored on carbon cloth through a facile hydrothermal method. Among tested electrocatalysts, P doped Co_1-xS exhibits excellent electrocatalytic performance with an overpotential of 110 and 165 mV (vs. RHE) for current densities of 10 and 100 mA·cm^-2, respectively. Density functional theory calculations reveal that P doped Co_1-xS possesses a smaller bandgap and more optimal hydrogen adsorption sites than pristine Co_1-xS. This work initially investigates various cobalt sulfides doped with P and further gets insight into the activity improvement mechanism of P doping, which could guide the design of earth-abundant HER electrocatalysts for the "hydrogen economy".